Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Power Switching Circuits for Coupled Ancillary Devices

IP.com Disclosure Number: IPCOM000037156D
Original Publication Date: 1989-Nov-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 4 page(s) / 67K

Publishing Venue

IBM

Related People

Powell, KE: AUTHOR [+2]

Abstract

A technique is described whereby power switching circuits of ancillary devices, as when coupled to computers, can be controlled from a single source. The concept is unique in that there is no series device between the power source and the load of the ancillary device. The concept enables time signals to be superimposed on the power lines to control various ancillary devices.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 4

Power Switching Circuits for Coupled Ancillary Devices

A technique is described whereby power switching circuits of ancillary devices, as when coupled to computers, can be controlled from a single source. The concept is unique in that there is no series device between the power source and the load of the ancillary device. The concept enables time signals to be superimposed on the power lines to control various ancillary devices.

In the prior art of controlling the power of ancillary devices, resistor 10, as shown in the circuit of Fig. 1, was placed in series with the primary power source and the load to serve as a voltage sampling element. The voltage was rectified through rectifier 11 to form the input reference voltage for control circuitry, usually through a relay. The relay, in turn, was used to control the primary power application to the ancillary device. The utilization of resistive element 10 can cause the current to the load to vary as ancillary devices are added, since the value of the resistor must be based on the load current involved. Therefore, difficulty arises in the ability to meet voltage margin specifications. Also, physical size and heat generation requirements must be considered.

(Image Omitted)

Prior art also utilized semiconductor devices, as shown in Fig. 2, whereby groups of silicon diodes, or zener diodes, 12 are placed in series with the load to form the desired level of voltage to the active control circuitry. The use of semiconductors of Fig. 2 has some advantages over the resistor technique of Fig. 1 in that the current drawn by the load devices has little effect on the voltage developed across the sampling element. This means that the load value is no longer critical and can vary to a large degree without any effect on the circuitry. However, the problem of meeting voltage margin specifications still exists in the effort to attain the desired level of voltage to activate the control circuitry. Also, the solid state circuitry presents a new problem, as outlined in the waveform of Fig. 3. Here the primary power is actually turned off for four periods during each AC cycle. The voltage value and the duration of each of the periods is determined by the value of the semiconductors chosen to furnish the necessary sampling voltage. In addition to the absence of power during the four periods of each cycle, it forms very steep wave fronts that can cause problems in both linear- and switching-type power supplies that are connected to the load side of the circuitry. Also, a very large increase in electro-magnetic interference (EMI) is generally encountered due to the wave form distortion....